Hearing devices are wearable hearing apparatuses which are used to assist the hard-of-hearing. In order to accommodate numerous individual requirements, various types of hearing devices are available such as behind-the-ear (BTE) hearing devices, hearing device with external receiver (RIC: receiver in the canal) and in-the-ear (ITE) hearing devices, for example also concha hearing devices or completely-in-the-canal (ITE, CIC) hearing devices. The hearing devices listed as examples are worn on the outer ear or in the auditory canal. Bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. The damaged hearing is thus stimulated either mechanically or electrically.
The key components of hearing devices are principally an input converter, an amplifier and an output converter. The input converter is normally a receiving transducer e.g. a microphone and/or an electromagnetic receiver, e.g. an induction coil. The output converter is most frequently realized as an electroacoustic converter e.g. a miniature loudspeaker, or as an electromechanical converter e.g. a bone conduction hearing aid. The amplifier is usually integrated into a signal processing unit. This basic configuration is illustrated in FIG. 1 using the example of a behind-the-ear hearing device. One or a plurality of microphones 2 for recording ambient sound are built into a hearing device housing 1 to be worn behind the ear. A signal processing unit 3 which is also integrated into the hearing device housing 1 processes and amplifies the microphone signals. The output signal for the signal processing unit 3 is transmitted to a loudspeaker or receiver 4, which outputs an acoustic signal. Sound is transmitted through a sound tube, which is affixed in the auditory canal by means of an otoplastic, to the device wearer's eardrum. Power for the hearing device and in particular for the signal processing unit 3 is supplied by means of a battery 5 which is also integrated in the hearing device housing 1.
A hearing device system for the binaural supply of a person who is hard of hearing includes two hearing devices, one of which is worn on the left ear and the other on the right ear. If the two hearing devices communicate with one another in any fashion (e.g. by way of a wireless connection), this is referred to as a “binaurally coupled hearing system”. A binaurally coupled hearing system of this type has the possibilities of spatial signal processing, which is not possible using a monaural system, since with this system signals can be transmitted from one side to the other.
Approaches to binaural beam forming algorithms (beam forming) or blind separation algorithms (blind source separation) are known from the literature for instance. The element common to these known algorithms is that the necessary transmission capacity of the connection between the two devices has to be comparatively high since in order to calculate the output signal on the one side, both the overall input signal of the same side and also that of the other side are needed. A correspondingly high data transmission rate is thus needed for broadband communication, which is disadvantageous in respect of the high energy consumption associated therewith in the case of hearing devices. Only monaural methods are known as alternatives, which however are restricted as a result of the very minimal microphone distances above all in the case of low frequencies. Methods for realizing a directional microphone, a blind source separation, a feedback coupling reduction etc. are affected for instance.
Monaural methods of this type comprising one, two or more microphones per side indicate very good properties in respect of their performances such as interference noise suppression and noise performance in the case of higher frequencies (>2 kHz). In the case of low frequencies, the noise problems occurring as a matter of principle (as a result of the inherent noise always present in the microphones in conjunction with the minimal microphone distance) nevertheless cannot continue.
The publication WO 99/431185 A1 discloses a binaural, digital hearing aid system, in which data is transmitted crosswise from the right to left and from the left to right hearing device. The data received by the other hearing device in each instance is processed binaurally using the actual data of the hearing device. If necessary, data is compressed prior to transmission.
The publication EP 1 771 038 A2 also discloses a method for operating a hearing aid device system for the binaural supply of a user. In frequency ranges, in which problematic feedback is to be expected, the input signals are transmitted crosswise to the other hearing device in each instance, so that an acoustic signal received by the microphone of a hearing aid device can be output via the receiver of the other hearing aid device in each instance following signal processing and amplification. As a result, the distance between a receiver and a microphone in each instance, between which a feedback path exists, is significantly increased for the relevant audio signals.
The publication WO 2004/114722 A1 also discloses a binaural hearing aid system with a coordinated sound processing. Here data relating to the classification of the sound environment is exchanged between both hearing devices.